He stays in shape and is ready for the rest of the season. I think he is the best pitcher of my lifetime, if not ever...
I do have to give him credit for that. Throughout his career he has taken conditioning very seriously which probably has a lot to do with why he has been resistant to having his arm constantly getting injured. The only other big name pitcher I can think of like that is Randy Johnson who was more of a 1 in 10,000 freak of nature where the abuse and pitch counts he racked up just didn't matter to him rather than being a conditioning maniac like Clemens is. Plus Johnson started pitching heavily at the age of 26, which probably helped him also.
I also think Clemens has cemented his spot of the greatest pitcher our generation has had. You would probably have to go back to early last century to find people comparable. There was a point where I would put him with Pedro, Randy Johnson, and Greg Maddux but I think he has pulled himself above that group. I would actually say he could be considered a "inner circle" hall of famer at this point, and if it wasn't for Mr. Potato head (aka Barry Bonds), Alex Rodriguez, and Mark McGwire you could make a case for him being the best player of our generation. (I counted people like Ricky Henderson as a little before my time).